dt-bindings: arm: stm32: Add Phytec STM32MP1 board

The Phytec STM32MP1 based SoMs feature up to 1 GB DDR3LP RAM, up to
1 GB eMMC, up to 16 MB QSPI and up to 128 GB NAND flash.
Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>

Documentation/devicetree/bindings/arm/stm32/stm32.yaml

@@ -155,6 +155,12 @@ properties:
           - const: seeed,stm32mp157c-odyssey-som
           - const: st,stm32mp157
 
+      - description: Phytec STM32MP1 SoM based Boards
+        items:
+          - const: phytec,phycore-stm32mp1-3
+          - const: phytec,phycore-stm32mp157c-som
+          - const: st,stm32mp157
+
 additionalProperties: true
 
 ...